I have a 2008 F150 5.4L 3V triton. 4wd, with 114k miles on it. About a month ago I put a 1.5" level kit on it and 35" tires.

My issue started when I, being a stupid youngin, gave it too much gas while going down a side road. I got it up to 4k rpms when i left off the gas. Nothing seemed to happen except the rpms seems to go down weird, but I continued driving. I stopped at a redlight, then when i got going, i felt a little jolt, and i figured that it was getting back into gear. as i was driving at a steady 30 mph at 1500 rpms, i began to hear grinding, i cant remember what area of the truck it was coming from, but it kind of sounded like it was coming from the under the cab, but im not entirely sure . i continued about a quarter mile when i had to stop at another red light. when I went to accelerate, there was a small jolt, then no power. i was giving it gas and it was barely moving.

once the tow truck came, we found out the truck would not roll backwards when in neutral. we threw it in reverse and it still wouldnt roll. we tried in every gear and it would not roll backwards. I put it in drive and gave it a lot of gas and it didnt budge, put it in 2nd gear, nothing, then 1st and still nothing.

I finally get it towed to my place. I did some tests, I put the truck in 4 wheel drive low, i was able to move it forward, but only a few inchs before i stopped it, but when i put it in reverse, it didnt budge. also when I was switching from 2wd to 4wd low i could hear the transfer case making a noise while switching to 4wd low and back. but it would switch to 2wd to 4wd no problem.

now from what I described, does it sound like a broken rear diff? or a broken transmission? or an broken transfer case?

 

I'm going to try and test the 4wd further when I get home from work, and i will update on what i get.

 

Not sure it will help but I had similar issues on my 1997 Ford F150 and it was due to the transfer case! It deteriorated to the point where I could not even use 4-wheel drive.